On the spatial development of the mixing layer at the interface between open water and a region containing emerged vegetation

In this paper, we investigate the flow in an open channel containing a rectangular array of emerged rigid square cylinders at one of its sides. The length of the porous patch is finite and its width is one third of the channel width. The cylinders are distributed fairly uniformly within the array and the solid volume fraction is SVF = 10%. This mimics the case of an emerged patch of vegetation present at one of the banks of an open channel. The size of the square cylinders in the array is d = 0.1D, where D is the water depth. The channel Reynolds number is 12,500. Detached Eddy Simulation (DES) is conducted to understand the vortical structure of the flow and the spatial development of the shallow mixing interface forming between the porous (vegetated) region and the open water region. The instantaneous flow fields show that the exchange at the interface between the two regions is far from uniform in the streamwise direction. Large-scale vortex shedding occurs especially in the wakes of the cylinders situated close to the interface between the porous region and the channel. Quasi-periodical large-scale unsteady motions are generated within the mixing interface, the porous patch and behind it. Similar to the case of a solid obstruction placed at one side of the channel, necklace vortices form around the extremity of the upstream leading edge of the porous patch. Finally, the streamwise evolution of the shallow mixing layer at the interface between the porous and open water regions is investigated based on the cross-stream distributions of the Turbulent Kinetic Energy (TKE).
4 International Conference on Fluvial Hydraulics, RIVER FLOW 2016


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Citation Formats
M. Köken, “On the spatial development of the mixing layer at the interface between open water and a region containing emerged vegetation,” presented at the 4 International Conference on Fluvial Hydraulics, RIVER FLOW 2016, St. Louis; United States, 2016, Accessed: 00, 2021. [Online]. Available: https://hdl.handle.net/11511/79263.